1. Field of the Invention
This invention relates to a head shifting device employed in a recording or reproducing apparatus which changes the recording or reproducing position thereof from one position to another by shifting a recording or reproducing head in the radial direction of a disc-shaped flexible recording medium.
2. Description of the Prior Art
Various magnetic recording or reproducing apparatuses have been known which record or reproduce a video signal of a still or slow motion picture, an audio signal, a data signal, or other information by bringing a magnetic head into contact with a flexible magnetic disc contained in a cassette. In the magnetic recording or reproducing apparatus of this kind, if the magnetic recording or reproducing apparatus is unused over a long period of time with the cassette left loaded on the apparatus, a portion of the magnetic disc in contact with the head tends to be permanently deformed by the protrudent state of the magnetic head or, in some cases, the head comes to stick to the disc because the magnetic head under that condition remain in contact with the flexible magnetic disc contained in the cassette. Then, if the magnetic disc is rotated in that state, the magnetic material on the recording surface of the magnetic disc would be peeled off. In recording, the peeled part becomes unrecordable. In reproduction, it becomes a video signal undetectable region and thus results in a signal drop-out.
To avoid this inconvenience, an arrangement has been proposed to have the head set in a specific position remote from the recording area on the magnetic disc when no recording or reproduction is to be performed over a long period of time.
However, the recordable density of signals on a magnetic disc has increased during recent years. As a result, the size of the magnetic disc is tending to become smaller. Therefore, even if the magnetic head is positioned outside of the recording area of the magnetic disc as mentioned above, a swelled portion of the disc which is formed with the head at the apex of the swell would spread to the recording area to cause a permanent deformation of the recording area.
In view of this, a method has been proposed to have the head set away from the magnetic disc in the specific position remote from the recording area on the magnetic disc when no recording or reproduction is to be performed over a long period. As an alternative, another method is also proposed to arrange the head to be movable back and forth relative to the disc in response to locking and unlocking operations of a recording operation member provided on the recording apparatus.
However, the former method requires shifting the head to a given position outside the recording area of the recording medium and then moving the head away from the medium or disc. This tends to result in a complex structural arrangement of a head shifting device or a complex control system for the device. Further, in recording or reproduction, the head must be shifted over a given distance to a required position. This impairs the promptness of the recording or reproducing operation. In the case of the latter method, the head shifting device must be provided with some arrangement to interlock the device with a lock device for the recording operation member. This requirement not only tends to result in a complex structural arrangement, but also presents another problem that the head would be left in contact with the recording medium if a locking operation is not performed as an oversight. Therefore, that method does not give a sufficient assurance for elimination of the inconvenience mentioned in the foregoing.